How do I tell my auntie

So I’m going to get straight to the point I’m 18 and I’ve been talking a lot to my aunties best friend lately, and we have both been flirting a lot and we both promised to keep it a secret as there is a big age gap 19 years I think so yes he’s double my age and the fact that he’s a close family friend but I found out that he’s told someone as they have messaged me saying that she knows about us. And I don’t want my auntie to find out yet but I feel like I should be the one to tell her. He also keeps asking for nudes which I don’t mind but I’m scared that something is going to happen and that my auntie won’t forgive me for getting involved with her best friends any help would be appreciate